The first two episodes of Xenosaga, Der Wille zur Macht and Jenseits von Gut und Böse, are released as a single game, adapted for a handheld platform.

Story-wise, the game is roughly the same as the console versions. The player starts as Shion Uzuki, testing the newly developed android KOS-MOS, proceeding through the plot all the way up to where Episode II ended.

Several cutscenes that were left out of the console release are featured, giving deeper insight into the personalities of the characters.

Xenosaga I & II replaces the original 3D world with 2D graphics and an isometric perspective for battles. Cutscenes are presented with anime-style character portraits with dialogue displayed in text boxes.

The battle system retains most of the defining features of Xenosaga: Episode I, including the boost system and A.G.W.S. combat.

Xenosaga I & II for the Nintendo DS remains exclusive to Japan.